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Article - Mortality trends among people aged 50 years and over

MORTALITY TRENDS OF PEOPLE AGED 50 YEARS AND OVER

Between the two three-year periods, 1970-72 and 2002-04, reductions in mortality of people aged 50 years and over have been responsible for 70% of the male and 73% of the female increase in life expectancy at birth.

Australians today are living longer than ever with life expectancies among the highest in the world. A boy born in the period 2002-04 could be expected to live on average to 78.1 years of age, while a girl could be expected to live to age 83.0 years, gains of 10.3 and 8.5 years respectively over the 32 years from 1970-72.

Increases in life expectancy are desirable insofar as they represent improving health and longevity of the population, but they also present challenges. Greater life expectancy, by definition, is a contributor to population ageing and has implications for future government spending in health and aged care, as well as provision of income for a potentially longer retirement.

Throughout the 20th century, significant gains were made in life expectancy of Australians. These gains can be viewed as having occurred in two broad phases. The first phase was driven by declines in infant and child mortality, while the second was driven primarily by reductions in death rates of people aged 50 years and over. The transition between the phases occurred just before the middle of the century (1946-48) for females and around 1970-72 for males. (End note 1)

The increase in life expectancy at birth since 1970-72 has resulted from reductions in death rates at all ages, although reductions in mortality of people aged 50 years and over have been responsible for 70% of male and 73% of female life expectancy improvement. This article examines the age-groups, and specific causes of death for each sex that have contributed to the increasing longevity of the population aged 50 years and over.

LIFE EXPECTANCY AND MORTALITY

Life expectancy and survival rates are based on life tables. Life tables are statistical models used to show the levels of mortality of a population at different ages. The two sets of life tables used in this article (1970-72 and 2002-04) are based on mortality rates for each of the three-year periods. The life table depicts the mortality experience of a hypothetical group of newborn babies throughout their entire lifetime. It is based on the assumption that this group is subject to the age-specific mortality rates of the three-year reference period.

Increases in life expectancy in the population result from overall reductions in death rates over time. A statistical method has been used to determine the age-groups' relative contribution to the improvement. (End note 2) The two critical factors determining the increase in life expectancy are the age at which reductions in deaths occur - the younger the reductions occur, the greater the average life-years to be lived in the future - and the absolute size of the reduction in death rates.

The 1970-72 life tables used in this analysis were prepared by the Australian Government Actuary (and published by the Australian Bureau of Statistics (ABS)), while the 2002-04 life tables were produced by the ABS. AGE GROUPS CONTRIBUTING TO INCREASED LIFE EXPECTANCY

In 2002-04 males aged 50 years could expect to live a further 31 years on average to age 81 years, an increase of 7.8 years over the 1970-72 life expectancy. The female life expectancy at 50 years of age increased by 6.5 years over the same period. In 2002-04 females aged 50 years could expect to live an extra 35 years to almost 85 years of age.

The gains in life expectancy at age 50 years for males were achieved predominantly through mortality declines at the younger end of the 50 years and over population, with 63% of the increase in life expectancy coming from those aged 50-69 years. In contrast, only 44% of the female increase in life expectancy came from mortality improvements of those aged from 50-69 years, with the majority of the gains (56%) being achieved through the mortality reductions of those aged 70 years and over (graph 9.8). The older age contribution for the female gain in life expectancy results from the female death rate being already quite low for those aged 50-69 years in 1970-72. Therefore, despite age-specific death rates for females aged 50-69 years more than halving over the 32 years to 2002-04, the absolute decline in death rates in that age group was not as influential in increasing female life expectancy as the decline in the death rates of women over 70 years of age.

SELECTED CAUSES OF DEATH AND THEIR CONTRIBUTION TO GAINS IN LIFE EXPECTANCY AT AGE 50 YEARS

In 1970-72, six specific causes of death were responsible for 80% of all deaths of people aged 50 years and over. In 2002-04, these same selected causes of death were responsible for 75% of all deaths of people aged 50 years and over. However, the death rates in the latter period were generally much lower than in 1970-72 with the all-cause standardised death rate falling by around half for both males (down 51%) and females (down 48%).

As would be expected, the causes of death with the highest death rates have a greater potential to contribute to improved life expectancy through their reduction than the less significant causes.

Reductions in deaths from ischaemic heart disease and cerebrovascular disease (stroke) have been key to improvements in life expectancy at age 50 years in recent decades. Reductions in associated risk factors and improvements in treatment and care have been instrumental in reducing deaths from these causes. On the other hand, the small overall declines in cancer death rates for people aged 50 years and over have not translated into significant gains in life expectancy.

DEATH RATES AND AGE-STANDARDISING

Death rates in this article use averages of three years of deaths data for each period (i.e. 1970-72 and 2002-04) and the estimated resident population for the middle year of each period as the death rate denominator.

Death rates used for comparisons of particular causes of death over time have been age-standardised. Age-standardising adjusts death rates to remove the effect of differing age structures of populations when making comparisons of death rates. The standard population used was the 2001 estimated resident population.

Analysis in this article uses the concept of the underlying cause of death. Underlying causes of death are classified by the disease or injury which initiated the train of morbid events leading directly to death. Cause of death data are obtained from the ABS Causes of Deaths collection and are presented according to the International Classification of Diseases, 10th revision (ICD-10). ABS publish comparability factors to account for the introduction of the Automated Coding System in 1997 and these have been applied to the 1970-72 deaths. (End note 3)

Ischaemic heart disease

In 2002-04 ischaemic heart disease accounted for one-fifth (20%) of deaths of people aged 50 years and over. In 1970-72, over one-third (35%) of deaths were attributed to ischaemic heart disease. The male and female standardised death rates for ischaemic heart disease of those aged 50 years and over fell by around two-thirds (70% and 68% respectively) (graph 9.10). For males aged 50 years, the result of this decrease has been a gain of 4 years of life expectancy (just over half of the total gain in the period). Females gained 2.9 years (or 45% of the total female increase in life expectancy at age 50 years) from declines in ischaemic heart disease death rates (graph 9.11).

Cerebrovascular disease

Cerebrovascular disease (stroke) was responsible for 10% of deaths of people aged 50 years and over in 2002-04 and 16% in 1970-72. Over the period, death rates also decreased dramatically with declines of 70% for males and 71% for females. These were estimated to have contributed 1.1 years to male and 1.8 years to female life expectancy at age 50 years in 2002-04.

Cancer

Cancer was the cause of more deaths than any other selected cause for people aged 50 years and over in 2002-04 with 29% of all deaths. In 1970-72 the proportion was 17%.

Compared with the other major causes of death, cancer death rates have declined relatively slowly. In the 32 years to 2002-04, the standardised death rates for people aged 50 years and over declined by only 6% for males and 4% for females. This small reduction in death rates was reflected in a minor contribution to increased life expectancy at age 50 years - around five months for males and two months for females.

Males had an 18% decrease in the lung cancer death rate over the 1970-72 to 2002-04 period, contributing around three months to male life expectancy at 50 years of age. Females, on the other hand, had an increase of more than two and half times (163%) in their lung cancer death rate, equivalent to almost a three-month reduction in life expectancy for women aged 50 years. This reflects an increase in smoking rates among women in the latter third of the 20th century.

Female breast cancer and colorectal cancer death rates declined by 13% and 37% respectively. Together they added around three months to life expectancy. Males also had a (17%) decline in colorectal cancer death rates, although the impact on life expectancy was less than one month.

Diseases of the respiratory system

Deaths from diseases of the respiratory system (mainly pneumonia and other obstructive pulmonary disease) made up 9% of all deaths in 2002-04 and 7% in 1970-72.

For males aged 50 years and over, the standardised death rate for diseases of the respiratory system decreased by 46% and contributed around eight months to male life expectancy at age 50 years. Among females however, there has been no reduction in the death rate from this cause. As with lung cancer, this may also be attributed to the increase in womens' smoking prevalence in the latter part of the 20th century.

Endocrine, nutritional and metabolic diseases

Deaths from endocrine, nutritional and metabolic diseases (mostly diabetes mellitus) was the underlying cause of 4% of deaths for people aged 50 years and over in 2002-04 and 2% in 1970-72.

Between age 50 and 79 years, males experienced a decline in the death rates for endocrine, nutritional and metabolic diseases, but this was offset by an increase in the death rate from age 80 years. Females had a similar pattern except the increase in the age-specific death rate was seen at age 85 years and over only. The impact on life expectancy at age 50 years for males was negligible, and only around two months for females.

External causes

External cause of death (accidents, poisonings and violence) contributed 3% of all deaths of people aged 50 years and over in 2002-04, and 4% in 1970-72.

The standardised death rate for this cause has halved for both males and females. As a lower order cause of death, however, the effect on life expectancy at age 50 has been small - around four months for both males and females. Suicide deaths contributed one-quarter (26%) of male external causes of death, although the rate was 39% less in 2002-04 than in 1970-72.

Projections

ABS has produced population projections from 2005 to 2101 that are underpinned by assumptions of future mortality in addition to fertility and overseas migration. The medium series projection assumes life expectancy will continue to increase until 2051 where males aged 50 years could expect to live to 86.6 years, while females aged 50 years could expect to live to 89.1 years (see Population projectionsin the Population chapter). These projections represent increases of 6.0 years for males and 4.5 years for females over the 47 years from 2002-04 to 2051 (graph 9.12). They also point to a halving of the rate of increase in life expectancy experienced over the last three decades. While the average rate of increase in life expectancy at age 50 years for males was 3.1 months per year between 1972 and 2002, between 2004 and 2051 it is assumed to increase by an average of around 1.5 months per year. For females the rate of increase in life expectancy at age 50 years averaged 2.6 months per year between 1972 and 2002, while the assumption over the 2004 and 2051 period is for an increase of 1.1 months per year.

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